In soil environments, the surfaces of clay minerals are often coated with hydrolytic products of Al. However, limited information is available on the effect of hydroxyaluminum coatings on the interlayering of enzymes for montmorillonite. The objective of this study was to compare the adsorption of tyrosinase onto montmorillonite as influenced by levels of hydroxyaluminum coatings. Tyrosinase is one of the strongest catalysts in the transformation of phenolic compounds. Adsorption of tyrosinase onto Ca-montmorillonite (Ca-Mte) and different hydroxyaluminum-montmorillomte complexes (Al(OH)x-Mte), containing 1.0, 2.5 and 5.0 mmol coated Al/g clay, was studied both in the absence and in the presence of a phosphate buffer at pH 6.5 and 25°C. Except for Ca-Mte in the absence of phosphate where the adsorption isotherm was of C type (linear), the adsorption isotherms were of L type (Langmuir). More tyrosinase molecules were adsorbed onto Ca-Mte than onto the Al(OH)x-Mte complexes, both in the absence and in the presence of phosphate. This indicated the easy accessibility of the enzyme to the uncoated Ca-Mte surfaces. The presence of phosphate did not significantly affect the amount of tyrosinase adsorbed onto Ca-Mte, but substantially reduced the adsorption of tyrosinase onto Al(OH)x-Mte complexes. The higher the level of hydroxyaluminum coatings, the lower the amount of tyrosinase was adsorbed. Because of their affinity to the aluminous surfaces, phosphate ions evidently competed strongly with tyrosinase for Al(OH)x-Mte complexes adsorption sites. The intercalation of tyrosinase by Ca-Mte was indicated by the increased d-spacing of the complex as the amount of the enzyme adsorbed increased. The infrared spectra of tyrosinase-Ca-Mte complex showed that the amide II band of tyrosinase at 1540 cm-1 was practically unaffected by adsorption. The amide I band at 1654 cm-1 was shifted toward a higher frequency, indicating a slight perturbation in the protein conformation. This perturbation became more noticeable in the presence of Al(OH)x-Mte complexes. The data indicated that hydroxyaluminum coatings play an important role in retarding the adsorption of tyrosinase by montmorillonite, and phosphate effectively competes with tyrosinase for the adsorption sites on Al(OH)x-Mte complexes.

Several samples of large- and small-particle magnetite (Fe3O4), as well as its thermal decomposition products formed at different temperatures and atmospheres, have been studied extensively by Mössbauer spectroscopy (MS), both with and without an applied field of 6T. Synthetic mixtures of magnetite and poorly- or well-crystallized maghemite have also been studied. Large-particle magnetite (MCD > 200 nm), when heated in air for 12 hours at T < 400°C, transforms to a mixture of well-crystallized hematite and magnetite, the latter one remaining stoichiometric, according to the relative area-ratios obtained from MS. Thermal treatment at 1300°C in a controlled O2 partial pressure, produced a mixture of stoichiometric and nonstoichiometric magnetite, but the latter component seems to be composed of particles with different degrees of nonstoichiometry. The Mössbauer spectra of the decomposition products at T < 200°C in air of small-particle magnetite (MCD ~ 80 nm) could be successfully interpreted as a mixture of magnetite and maghemite, rather than nonstoichiometric magnetite. This suggestion is further supported by the experiments with the synthetic mixtures. It is clearly demonstrated that is not possible, even by applying a strong external field, to separate the contribution of the A-site of magnetite from that of maghemite.

Hydraulic conductivity tests were conducted on thirteen compacted clayey soils being used for compacted clay liners at landfills throughout the United States. The soils were prepared to various molding water contents and then compacted and permeated in the laboratory. Results of the tests show that for all of the soils, zones exist in the compaction plane (i.e., dry unit weight vs. water content) where the hydraulic conductivity is similar. These zones fall roughly parallel to contours of constant initial saturation (degree of saturation at compaction), with lower hydraulic conductivities generally occurring for conditions corresponding to higher initial saturation. Wet of the line of optimums, lower hydraulic conductivity is also attained for soils that are more plastic and have a greater quantity of fines. A regression equation was developed from the data to estimate hydraulic conductivity given the initial saturation, compactive effort, plasticity index, and clay content.

The mode of growth of authigenic, lath-shaped illitic particles has been investigated using field emission scanning electron microscopy (FESEM) and high resolution transmission electron microscopy (HRTEM). Two types of clay lath have been identified: overgrowths on platelets of illite or illite-smectite and discrete particles. Both are neoformed and show a slight increase in abundance with depth over the 70 m depth interval sampled. Interpretation of lattice fringe data is not unambiguous but indicates that the clay is either illite or illite-smectite with R1 structure. The formation of discrete particles of authigenic illite, or even R1 illite-smectite, is compatible with present burial depths and a regional geothermal gradient of approximately 40°C/km. This illite also differs from many previous reported occurrences of authigenic illite in mudrocks in that it appears to have formed, without being preceded by progressive illitization of illite-smectite.

The effect of cooling rate on the formation of smectite crystals with high crystallinity was investigated using two different types of high-pressure and high-temperature apparatus, a modified belt type and a uniaxial split-sphere type. The cooling rate was changed after a treatment of the sample at 5.5 GPa and 1500°C. Smectite crystals were obtained at faster cooling rate, coexisting with coesite, kyanite, jadeite, corundum and/or glass. In the slowly cooled process, no smectite crystals were obtained but coesite, kyanite, jadeite and clinoenstatite were formed. These results indicate that smectite crystals are formed metastably during the quenching of the high-pressure and high-temperature hydrous silicate melt.

A series of natural clays, including 1:1 layer silicates (serpentines, kaolin minerals), smectites, vermiculite, micas, talc, pyrophyllite, sepiolite, and palygorskite, were studied by 19F magic-angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy. The 19F chemical shift in these layer silicates is characteristic of the structure, in particular, to the local octahedral cation occupancy. Fluoride ions bonded to three Mg octahedral cations have a chemical shift of about −177 ppm and those bonded to two Al cations and a vacancy have a chemical shift of about −134 parts per million (ppm). The shift at −182.8 ppm in hectorite is apparently associated with fluoride bonded to two Al cations and a Li cation. Surprisingly, the difference in chemical shift of the interlayer and inner fluoride in 1:1 layer silicates is insufficient to distinguish these sites. Based on trends in chemical shift, it appears that fluoride substitution for inner hydroxyls in clays with octahedral substitution is not random. Fluoride is apparently preferentially associated with Mg rather than Al in the octahedral sheet as no resonance due to a fluoride bonded to two Al cations and a vacancy is observed in clays such as SAz-1.

Upper Cretaceous-Tertiary marine clayey-calcareous rocks of the Hekimhan basin contain fibrous clay minerals in significant amounts. Ophiolitic rocks in the provenance area have contributed the elements to form the clay minerals. XRD, SEM, major, trace and REE analyses were applied to samples taken from several stratigraphic sections. Diagenetic minerals such as smectite, dolomite, calcite, gypsum, celestite and quartz/chalcedony are associated with sepiolite-palygorskite group clays. Trace and rare earth elements (REE) are more abundant in palygorskite than sepiolite. REE abundances in the sepiolite-palygorskite are characterized by negative Eu and positive Nd anomalies when normalized with respect to chondrite and shale. Sepiolites with sharp XRD peaks are formed by diagenetic replacement of dolomite and diagenetic transformation of palygorskite, or by direct crystallization from solution. The average structural formula of the sepiolite is:

(Mg7.15Al0.13Fe0.31Cr0.06Ni0.04)(Si11.98Al0.02)O30(OH)4(OH2)4Ca0.03Na0.02K0.02.8H2O

Palygorskite appears to be authigenic by direct precipitation from solution. It exists in both monoclinic and orthorhombic forms with the mean structural formula given below

(Mg2.22Al1.00Ti0.04Fe0.77Cr0.01Ni0.02)(Si7.68Al0.32)O20(OH)2(OH2)4Ca0.07Na0.05K0.10.4H2O

An improved model for the interpretation of thermal effects during dehydroxylation in aluminous dioctahedral 2:1 layer phyllosilicates considers trans-vacant (tv) and cis-vacant (cv) 2:1 layers and leads to very different temperatures of dehydroxylation for these tv and cv vacant modifications. In particular, smectites and illites consisting of cv 2:1 layers are characterized by dehydroxylated temperatures which are higher by 150°C to 200°C than those for the same minerals consisting of the tv 2:1 layers. A considerable lengthening of the OH-OH edges in cv 2:1 layers in comparison with the OH-OH edges in the tv 2:1 layers is postulated as the reason for the higher dehydroxylation.

Dehydroxylation in aluminous cv 2:1 layer silicates should occur in two stages. Initially, each two adjacent OH groups are replaced by a residual oxygen atom and the Al cations, which originally occupied cis -and trans-sites, become 5- and 6-coordinated, respectively. The structure of 2:1 layers corresponding to this stage of the dehydroxylation is unstable. Thus the Al cations migrate from the former trans-sites to vacant pentagonal prisms. The resulting dehydroxylated structure of the original cv 2:1 layers is similar to that of the former tv 2:1 layers.

Diffraction and structural features of the cv dehydroxylates predicted by the model are in agreement with X-ray diffraction effects observed for cv illite, illite-smectite and montmorillonite samples heated to different temperatures. In particular, the diffusion of Al cations to empty five-fold prisms during dehydroxylation of the tv 2:1 layers explains why dehydroxylation of reheated cv montmorillonites occurs at temperatures lower by 150°C to 200°C than samples that were not recycled.

Cation exchange experiments were carried out on phlogopite, biotite, and muscovite using cryptand [222] as a complexing agent, dioxane as solvent, and Li as the exchanging cation. The results indicate greater than 90% exchange of the analyzed cations K+, Rb+, and Sr++ in phlogopite and biotite after two days. Similar results for the exchange in muscovite are observed but it is apparently slower. The amount of exchange observed for mica depends mainly on pH, time and the exchanging cation at a constant temperature. Residues of the mineral phase were also investigated by X-ray diffraction and a significant change of the interlayer spacing was detected. Some samples of the residue were analyzed for Li content. The compositions of the treated samples were in good agreement with the determined exchange of K+.

Cu montmorillonite heated with or without potassium halide was studied by IR and ESR spectroscopy, supplemented by XRD measurements, microprobe and chemical analyses. It appears that on heating Cu montmorillonite, most of the Cu ions migrate into hexagonal cavities and eventually, when dehydroxylation occurs, into octahedral vacancies. Some Cu ions may penetrate into octahedral vacancies before dehydroxylation. In the presence of potassium halide, deprotonation facilitates penetration of Cu into octahedral vacancies. The presence within the layers of non-exchangeable Cu ions that are inaccessible to water does not necessarily cause the perturbation of OH bending vibrations conventionally attributed to migration of small cations into the structure. Such perturbation was only observed when the basal spacing was reduced to ~9.5Å.